The present invention relates to a sheet refeeding apparatus for use in combination with an image forming system such as a copying machine, for feeding a sheet repeatedly to the image forming unit of the image forming system for a multistage copying process such as a composite copying process in which a plurality of images are formed on one side of the sheet or a two-side copying process in which images are formed on both sides of the sheet.
There has been proposed a multipurpose copying machine capable of multistage copying processes including a composite copying process and a two-side copying process in addition to an ordinary single-side copying process. In a multistage copying process on such a conventional multipurpose copying machine, a sheet which has been subjected to an automatic copying process is guided to a secondary sheet conveying path extending from the sheet discharge section to the sheet feed section in addition to a main sheet conveying path extending from the sheet feed section to the sheet discharge section, and then the same sheet is fed again to the copying unit for another automatic copying process. There has been proposed a sheet refeeding apparatus for use in combination with such a multipurpose copying machine. This conventional sheet refeeding apparatus has an internal secondary sheet conveying mechanism for refeeding a sheet to such a multipurpose copying machine and is adapted for connection to the multipurpose copying machine as an additional unit. Generally, such a sheet refeeding apparatus further includes a sorter, a cabinet and related mechanisms and is provided with individual driving means for driving the secondary sheet conveying mechanism to convey a sheet through the secondary sheet conveying path thereof. The secondary sheet mechanism needs to operate synchronously with the main sheet conveying mechanism of the associated copying machine at the same operating speed as that of the main sheet conveying mechanism for a smooth and efficient conveyance of the sheet.
However, the conventional sheet refeeding apparatus is intended for use in combination with a particular copying machine and is unable to be used in combination with copying machines of different types. Accordingly, when the design and/or operating conditions of the copying machine are changed to update the copying machine, the sheet refeeding apparatus is unable to be combined with the newly developed copying machine. Therefore, the sheet, refeeding apparatus needs to be changed for another sheet refeeding apparatus machine is replaced with a newly developed copying machine, which imposes an additional expenditure on the user. Thus, the conventional sheet refeeding apparatus is designed for use in combination with a specific type of copying machine and hence is unable to be combined with general copying machines. Accordingly, the conventional sheet refeeding apparatus is economically disadvantageous, and is costly because the sheet refeeding apparatus is designed and manufactured specially for a specific copying machine.